Comparison of the Microwave-Heated Ziehl-Neelsen Stain and Conventional Ziehl-Neelsen Method in the Detection of Acid-Fast Bacilli in Lymph Node Biopsies

BACKGROUND: Tuberculosis is a chronic inflammatory disease with lymphadenopathy being the most common extra-pulmonary manifestation. The conventional Ziehl–Neelsen method plays an essential role in the diagnosis of tuberculosis; however, it has a low sensitivity in detecting acid-fast bacilli. AIM: The present study emphasises the role of the microwave-heated method (modified Ziehl–Neelsen) over conventional Ziehl-Neelsen stain and to set at the best condition for irradiation. MATERIAL AND METHODS: The study included 90 patients with clinically suspected tuberculous lymphadenopathy who were referred to the Department of Pathology at Omdurman Military Hospital, Sudan. Demographic data such as age, sex, and site of swelling were documented for each patient. Specimens were stained with conventional Ziehl-Neelsen, fluoresce and the modified methods. RESULTS: Patient’s age ranged from 20 to 70 year. Of the total 90 cases with clinically suspected tuberculous lymphadenopathy, 18 cases were positive for AFB in conventional Ziehl-Neelsen method giving a sensitivity of 13.3%, while in microwave-heated method 82 cases of TB were detected positive for AFB yielded sensitivity and specificity of 97.6% and 85.7%, respectively, and positive and negative predictive values of 98.8% and 75.0% respectively compared to fluorescence methods. CONCLUSION: In the present study, the microwave-heated Ziehl-Neelsen method, was found to have sensitivity and specificity of 97.6% and 85.7%, respectively which matches the fluorescence technique. It has specificity in detecting lymph node tuberculosis that makes it superior over all other modified methods. However, the availability and cost-effectiveness might limit the use of fluorescence in routine practice. Furthermore, the study set the best staining temperature is provided at power 1 level (60 w) for 1.5 minutes.